Newly-discovered extinct whale may have been the heaviest animal ever

Perucetus colossus, whose fossils were discovered in Peru, may be the heaviest discovered animal ever, even heavier than the blue whale.

Perucetus colossus, an extinct giant marine mammal heavier than the blue whale

Artist's reconstruction of Perucetus colossus, or the "colossal whale from Peru." (Alberto Gennari / Nature)

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Blue whales, the giants of the ocean, are known to measure as long as 29.9 metres and weigh as much as 180,000 kilograms—which is about the same as 36 of the heaviest Indian elephants you can find. But it may no longer be the heaviest animal that ever lived. There is a new contender for that post—Perucetus colossus.

Based on a newly-described fossil of the whale Perucetus colossus dating to more than 38 million years ago, scientists believe that it may have been heavier than a blue whale even though it may not have been as long, according to Nature. 13 vertebrae, 4 ribs and a bit of a pelvis of the gigantic sea creature were discovered in Peru. Researchers guess that the species weighed between 85 and a simply massive 340 tonnes.

The animal’s bones had an unusually large volume and were also extremely dense, according to Reuters. This combination of thickening and densification of bones is called pachyosteosclerosis. The characteristic is absent in living whales, dolphins and porpoise. But it is present in sirenians, a marine mammal group that includes sea cows. The animal has been described in an article published in the journal Nature.

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Whales that dive deep typically have the ability to completely empty their lungs to plummet into the depths of the ocean but P. colossus probably lived in shallow coastal areas. This would mean that it probably dived with air in its lungs. But diving with air in the lungs would make it quite difficult to stay near the seafloor—that is where the very heavy bones come in. The skeletal mass of P. colossus would have been between five and eight tons, which is twice that of the blue whale.

“Its fat, bloated body may have been more like that of a sirenian than of any living whale. Among sirenians, due to its giant size and probable similar lifestyle, it could recall Steller’s sea cow, discovered in 1741 and exterminated by humans a few years later,” Giovanni Bianucci, lead author of the study, to Reuters. Bianucci is a palaeontologist at the University of Pisa in Italy.